Conventionally, an activation control device for an airbag device includes; a floor sensor (deceleration sensor) disposed at the midsection of the vehicle body, and a satellite sensor (deceleration sensor) disposed at the front of the vehicle body, and a main control section determines a collision state of the vehicle based on an output signal of each of the sensors, to thereby control the activation of the airbag device. The floor sensor is generally disposed near the main control section, and the output signal thereof is transmitted directly to the main control section. Alternatively, the floor sensor is built into the main control section. The main control section, is, for example, disposed near the center console.
On the other hand, the satellite sensor is, for example, disposed near the front bumper, and the output signal thereof is transmitted to the main control section through a communication cable. For example, the satellite sensor digitizes a detection signal, and constantly transmits the digital signal thereof to the main control section. Furthermore, there is also an arrangement where the satellite sensor has a previously set threshold, and when the detected deceleration exceeds the threshold, an output signal indicating that the threshold has been exceeded is transmitted to the main control section (refer for example to Japanese Unexamined Patent Application, First Publication No. H11-59322).
For the communication method between the satellite sensor and the main control section, a serial communication method is used, from reasons such as decreasing the number of cables installed in the vehicle.
However, in the aforementioned conventional device where the satellite sensor continuously transmits output signals to the main control section, there is a problem in that if a plurality of satellite sensors is installed, the communication traffic increases, making multiplex transmission through serial communication difficult. Particularly in recent years, vehicle body construction where the crushable zone is reduced and the vehicle body hardness is increased, in order to expand the compartment (cabin) section, is increasing. In such a vehicle body construction, there is a need to determine the collision states, such as offset collisions and low speed collisions, with good accuracy. For this reason, a plurality of satellite sensors are disposed on the vehicle, such as at the front right, the front left, and on the left and right sides. However, with conventional devices, it is difficult to correspond to these.
On the other hand, in a device where the satellite sensors are made to hold a previously set threshold, and when the detected deceleration exceeds that threshold, an output signal indicating that the threshold has been exceeded is transmitted to the main control section, the communication traffic is decreased, thus solving the problem of traffic load. However, to determine the collision state with good accuracy, it is necessary for the threshold to be an optimal value depending on the position in which the satellite sensor is disposed. Therefore, it is necessary to construct satellite sensors holding every type of threshold. Furthermore, the threshold is different for each type of vehicle and its destination (delivery). Therefore, the number of types of satellite sensor becomes enormous.
In the case where in this manner very many types of satellite sensor are manufactured, there is a problem in that manufacturing management costs become large, becoming a liability.